Start of the Subway Series, coming back home after a draining road trip, and the Yankees had to bench their hottest hitter.

“Joe [Girardi] thought this was a good opportunity to take a day off it and make sure that I’m good to go,” Mark Teixeira said Monday afternoon at Yankee Stadium.

Yup, it’s early still, and the AL East appears surprisingly mediocre in what we’ve seen. Yet even a $500 million offseason infusion didn’t give the Yankees protection against their greatest weakness, again.

Their old age still lurks around every corner.

“You just take for granted your health [when you’re younger],” said Teixeira, who was bothered by a sore left groin. “People ask me, is it a physical or mental thing? It’s definitely a physical thing.”

Teixeira, who turned 34 last month, of course missed nearly all of last season with a right wrist injury, and then went on the disabled list with a right hamstring injury he sustained in Game 4 of this campaign. He has rebounded impressively, putting up a .266/.383/.557 slash line in 94 plate appearances and helping the Yankees tread water. But now we’ll see if this ailment costs him just the one game, as he hopes, or more.

Moreover, CC Sabathia, who turns 34 in July, is headed to noted orthopedist James Andrews to have his right knee examined. We’ll see if this injury costs the big lefty just 15 days on the disabled list or far more. We’ll also see, eventually, whether Sabathia can work his way back to being even a No. 3 or No. 4 starting pitcher, instead of the awful performer he has been for the better part of the past year and change.

We’ll see, too, whether retiring captain Derek Jeter, 39, can find one more fountain of youth so that his exit won’t turn painful, both physically and mentally. And whether Carlos Beltran, 37, and Alfonso Soriano, 38, have more to give, as neither has played anywhere close to his past performance level.

(For what it’s worth, Beltran has hit considerably better while serving as designated hitter as opposed to starting in the outfield, and it’s just the opposite for Soriano. On Monday, Girardi started Soriano in rightfield and Beltran at DH.)

In the wake of last year’s disastrous results, the Yankees worked diligently and spent generously over the winter to add some fresh blood. Their most expensive addition, pitcher Masahiro Tanaka, has exceeded their wildest dreams, putting up a 2.57 ERA and recording zero losses in his seven starts. Wednesday’s Subway Series pitting Tanaka against the Mets’ debuting Rafael Montero will give this interleague, intra-city matchup the most juice we’ve experienced in quite a few years.

It’s fitting, if not fully causative, that Tanaka, 25, arrived as the youngest of the Yankees’ four newcomers, well behind Beltran and 30-year-olds Jacoby Ellsbury and Brian McCann. Of that position-playing trio, only Ellsbury has performed at an acceptable level to date, presenting with the Yankees with an unpalatable scenario to envision: At least Sabathia and Teixeira reaped dividends in the early years of their megadeals, and even A.J. Burnett contributed some. What if this latest big buy doesn’t pay off early, and then bites the Yankees late as has been the case with their previous investments?

If the Yankees are to climb out of their current morass this season, they’ll have to lean most heavily on the guys still in their primes. On Ellsbury and McCann, and on the currently injured Michael Pineda, who provided so much hope with his early starts before revealing himself to be both remarkably stupid and unsurprisingly fragile within about a week’s time.

It’s not reasonable or realistic to expect Jeter to approach the heights of even recent years, not after his traumatic left ankle injury of 2012. Same goes for Teixeira, who likely can’t sustain his hot streak, and Sabathia.
You can’t outrun old age. You can only hope to minimize its importance. And the Yankees haven’t accomplished that mission yet.